The present invention relates to new ectoparasiticide-containing polyurethanes which contain spreading agents and ectoparasiticides or mixtures of ectoparasiticides, and to sheets, films, shaped articles, coatings or impregnations consisting of such polyurethanes and the use thereof in combating ectoparasites.
The commercially available PVC systems which have an ectoparasiticidal action and have hitherto been described, for example in the form of collars for small animals, generally consist of thermoplastic polyvinyl chloride into which an insecticidal or ectoparasiticidal active compound, for example O,O-dimethyl dichlorovinyl phosphate, has been incorporated by co-extrusion. PVC systems having this formulation occasionally lead to damage to the skin of the animal; another disadvantage is the short effective life of the collar formed of such PVC systems as a result of the relatively high vapour pressure of O,O-dimethyl dichlorovinyl phosphate (1.2.times.10.sup.-1 mm Hg).
Animal collars which are based on plasticised, thermoplastic polymers, preferably plasticised polyvinyl chloride, and which contain, as insecticidal active compounds, carbamates which have a lower volatility are described in U.S. Pat. No. 3,852,416. Whilst highly volatile active compounds, such as O,O-dimethyl dichlorovinyl phosphate rapidly pass directly into the gas phase from the ectoparasiticidally active plastic collars known hitherto, insecticides with a lower volatility, such as the carbamates mentioned, diffuse slowly out of the collar and form a white, dust-like layer on its surface. Some of the active compound passes into the vapour phase by sublimation and is effective in this phase, and another portion is distributed as a dust over the animal to be treated.
The said effluorescence or exudation of the active compound at the surface of the PVC system has a number of disadvantages.
If the PVC system is stored for a prolonged period before use, a relatively large amount of the active compound diffuses to the surface and becomes concentrated there. When the collar is used, there is then a very high dose of the insecticide on the surface, which indeed ensures a good immediate action but may already be at the limit of toxicity for the animal.
The active compound present on the surface is rapidly rubbed off. However, the active substance within the lower layers of the collar subsequently diffuses to the surface only very slowly. Release of the insecticide thus does not take place in the desired manner, that is to say uniformly over as long a period as possible.
The dust-like, whitish active compound present on the surface of the PVC system further imparts an extremely unattractive, dusty or mouldy appearance to the latter.
In the case of O,O-dimethyl dichlorovinyl phosphate and in the case of carbamates, the release of active compound is influenced by the plasticisers customary in PVC, such as phthalates and adipates.
The abovementioned difficulties can be avoided if polyurethanes which cannot be swollen in water and which contain certain amounts of spreading agents are used as carriers for the various ectoparasiticides or combinations thereof.
Spreading oils are understood as those oily liquids which spread particularly well on the skin. They are known as such in the cosmetics industry. According to a proposal by R. Keymer, Pharm. Ind. 32, 577, (1970), they can be characterised, for example, by their surface tension towards air and this should be between 20 and less than 30 dynes/cm.